Food and Behaviour Research

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Serum n3 polyunsaturated fatty acids are depleted in Crohn's disease.

Kuroki F, Iida M, Matsumoto T, Aoyagi K, Kanamoto K, Fujishima M. (1997) Digestive Diseases and Sciences 42(6) 1137-41. 

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To determine fatty acid patterns in Crohn's disease, we measured various serum fatty acids by gas chromatography in 20 patients with the disease and compared them with those in 18 healthy controls. All the patients had been free from any nutritional supplementation during preceding six months or had no history of intestinal resection. Eight of the patients were affected in the small bowel only, three in the large bowel only, and the remaining nine in both the small and large bowel.

Both serum concentrations and percentages of C20:4n6, C20:5n3, C22:0, C22:6n3, total n3 polyunsaturated fatty acids, and total polyunsaturated fatty acids were lower in the patients than in the controls.

Both essential fatty acids (C18:2n6, C18:3n3) and C20:3n9 levels were not different between the two groups.

Among nine fatty acids that correlated with the Crohn's disease activity index, C20:5n3 and total n3 polyunsaturated fatty acids showed the most significant negative correlations.

These findings suggest that essential fatty acid deficiency rarely occurs in Crohn's disease and also that n3 polyunsaturated fatty acids may be relevant to the activity of the disease.


Crohn's disease is an auto-immune condition that damages the gut lining.  Both omega-3 and omega-6 polyunsaturated fatty acids (PUFA) are important in regulating immune function, so blood levels of these and other fatty acids were investigated in Crohn's patients and controls.

No group differences were found in the shortest-chain omega-3 and omega-6 fats. These are known as dietary essential fatty acids (EFA), because in theory, they can be converted within the body into the longer-chain, more highly unsaturated omega-3 and omega-6 (LC-PUFA, or HUFA) - which are the most biologically essential, and the ones important for immune regulation.

By contrast, Crohn's patients did show significant reductions in blood levels of the main LC-PUFA - both omega-6 AA (20:4n-6), and the long-chain omega-3 (EPA and DHA).  Long-chain omega-3 and total omega-3 fatty acids were the ones most strongly (and inversely) related to Crohn's disease.

These findings suggest there may be poor conversion of short- to long-chain omega-3 and omega-6 in Crohn's disease.  In addition, the relative deficiency in omega-3, and the omega-3 LC-PUFA EPA in particular, may be relevant to the inflammation associated with this condition, as EPA is a substrate for important anti-inflammatory substances.